Gas distribution systems, in particular natural gas distribution systems, typically transport gas from a producer to a consumer along a series of pipes and through a series of valves. Each gas distribution system may include one or more regulator valves that control the pressure of the gas within the distribution system. Normally, the gas is transmitted at a high pressure through the system. However, the pressure of the gas must be reduced prior to final distribution to the consumers. This pressure reduction is typically accomplished at pressure reducing stations within local networks.
Typically, these pressure reducing stations include some sort of safety device to shut off the flow of gas. Most commonly, emergency shut-off valves are used for this purpose. The emergency shut-off valve is generally disposed upstream of the pressure regulating valve so that the emergency shut-off valve may prevent gas from reaching the pressure regulating valve in the event of a problem. The emergency shut-off valve can be operated manually, or can monitor gas pressure downstream of the pressure regulating valve, to close the valve and cut off the flow of gas to the pressure regulating valve to prevent an uncontrolled leak of gas, such as due to a pressure regulating valve failure or other problem.
Typically, emergency shut-off valves have a poppet or other type of valve plug that is mounted on a rotatable shaft to move the poppet between an open position, which allows the flow of fluid through the valve, and a closed position, which prevents the flow of fluid through the valve. However, in typical emergency shut-off valves, once assembled there is nothing preventing the poppet from sliding off of the shaft during maintenance. Therefore, if the shaft is moved during a maintenance procedure, there is the possibility that the poppet can drop into the valve, or even drop further down into the gas distribution system, which can require the removal of the emergency shut-off valve and cause other problems.
In addition, during assembly and maintenance of an emergency shut-off valve, one end of a torsion spring, which is used to bias the poppet into the closed position, must be aligned with and engage the gland to secure the end of the torsion spring. In typical designs, aligning the end of the torsion spring and ensuring engagement can be difficult when inserting the gland into the housing of the valve.
Finally, most typical emergency shut-off valves use a gasket between an outer surface of the gland and an inner surface of the valve housing to prevent leakage between the gland and housing. However, these gaskets are prone to leakage and problems can be encountered in installing these gaskets, especially if the gaskets need to be installed over threads, which can damage the gasket.